Low drag flameholder

ABSTRACT

A flameholder formed of two streamlined bodies separated by a gap forming spacer. The combustible fuel fed upstream of the flameholder fills the gap where it is ignited with the gap acting as a piloting zone continuously igniting the flowing mixture which is replenished.

United States Patent [191 Hall [ Oct. 21, 1975 LOW DRAG FLAMEHOLDER [75]Inventor: Patrick H. Hall, China Lake, Calif.

[73] Assignee: The Unites States of America as represented by theSecretary of the Navy, Washington, DC.

22 Filed: Feb. 2, 1972 21 Appl. No.: 222,853

[52] US. Cl 60/39.72 R; 60/3974 R; 431/350 [51] Int. Cl. F02C 7/22 [58]Field of Search 60/3972 R, 39.74 R; 431/350 [56] References Cited UNITEDSTATES PATENTS 2,625,795 1/1953 Brzozowski 60/3972 R 2,692,480 10/1954Viaud et al. 60/39.72 R

2,715,813 8/1955 Holmes et al. 60/3974 R 2,955,419 10/1960 Malick60/3972 R X AlRFLOW 3,300,976 l/1967 Coplin 60/3974 R X 3,328,958 7/1967Canuel. 60/3972 R 3,455,108 7/1969 Clare et al. 60/3972 R 3,465,5259/1969 Cowley et al. 60/3972 R X 3,605,407 9/1971 Bryce 60/3972 R3,701,255 10/1972 Markowski 60/3972 R Primary Examiner-C. J. HusarAssistant Examiner-Robert E. Garrett Attorney, Agent, or Firm-R. S,Sciascia; Roy Miller; Robert F. Beers [57] ABSTRACT A flameholder formedof two streamlined bodies separated by a gap forming spacer. Thecombustible fuel fed upstream of the flameholder fills the gap where itis ignited with the gap acting as a piloting zone continuously ignitingthe flowing mixture which is replenished.

1 Claim, 1 Drawing Figure US. Patent Oct.21, 1975 3,913,319

LOW DRAG FLAMEHOLDER BACKGROUND OF THE INVENTION 1. Field of theInvention.

This invention pertains to flameholders for holding a piloting flame ina combustor.

2. Description of the Prior Art.

In the past, recirculation zones for flameholding have been created bythe use of a bluff body. The bluff body has a separation andrecirculation zone in its near wake. The bluff body is a high dragdevice and the size of the unconfined recirculation zone is dependent onlocal flow conditions and is inherently unsteady due to the nature ofthe vortex shedding.

The primary advantage of the invention is that the flameholding zone isprovided by a shape that is low in drag. The drag is low because the gapis always filled, hence the mixture flow sees essentially anaerodynamically smooth configuration. Since the recirculation zone isconstrained to be of a constant size, this flameholder will operate overa wide range of flow conditions.

SUMMARY OF THE INVENTION An object of this invention is to create astable recirculation zone to hold a piloting flame in a ramjetcombustor.

The invention is a fiameholder of a generally spheroidal configurationformed of two streamlined bodies separated by a gap-forming spacer. Thecombustible fuel which comes from upstream of the fiameholder fills thegap where it is ignited. The gap acts as a piloting zone by continuouslyigniting the flowing fuel mixture which is replenished by a scavengingprocess.

BRIEF DESCRIPTION OF THE DRAWING The FIGURE shows a side elevationalview of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT The invention comprises forwardand rearward streamlined bodies of revolution 1 and 2, respectively,separated by spacer 3. This results in a generally spheroidalconfiguration of the invention with a gap between bodies 1 and 2. Theflameholder is fastened to a combustor wall by one or more streamlinedstruts 4.

Fuel flows through the strut via conduit 7, indicated by dashed lines,in the direction of the arrows. The fuel is introduced into thecombustor through injector 6 in a direction opposite to the air flow.

The fuel mixes with the air in such a way that a combustible mixtureresults. This mixture is carried down stream and fills the gap orrecirculation zone between bodies 1 and 2 where it is ignited. As thefuel-air mixture flows over the gap a scavenging process takes place atthe boundary between the flowing mixture and the stagnant gases in thegap thus replenishing the mixture that is burned in the gap. The gapthen acts as a piloting zone, continuously igniting the flowing mixtureand at the same time being replenished by it.

What is claimed is:

l. A fiameholder for use in a combustor comprising:

first and second streamline paraboloidal shaped bodies each having avertex and an end surface portion;

cylindrical spacer having its diameter substantially smaller than thediameter of said end portions and positioned between said first andsecond bodies with the flat surface ends of said spacer in contact withthe end surface of the first and second bodies to form a substantial gaptherebetween;

. a streamline strut attached to one of said bodies for holding saidfiameholder in spaced relationship to the wall of a combuster with thelongitudinal axis of said flameholder parallel to air flow through thecombustor; and

a fuel conduit extending through said strut and through the axis of atleast one of said bodies to terminate at the vertex of said body on theupstream side of the air flow;

whereby flow of fuel through the conduit exits into the air stream atthe vertex forming a combustible mixture that is carried over thesurface of the upstream body to the gap area to replenish the mixture ofgases within the gap establishing a stable recirculation zone at apiloting flame.

1. A flameholder for use in a combustor comprising: FIRST AND SECOND STREAMLINE PARABOLOIDAL SHAPED BODIES EACH HAVING A VERTEX AND AN END SURFACE PORTION; CYLINDRICAL SPACER HAVING ITS DIAMETER SUBSTANTIALLY SMALLER THAN THE DIAMETER OF SAID END PORTIONS AND POSITIONED BETWEEN SAID FIRST AND SECOND BODIES WITH THE FLAT SURFACE ENDS OF SAID SPACER IN CONTACT WITH THE END SURFACE OF THE FIRST AND SECOND BODIES TO FORM A SUBSTANTIAL GAP THEREBETWEEN; A STREAMLINE STRUT ATTACHED TO ONE OF SAID BODIES FOR HOLDING SAID FLAMEHOLDER IN SPACED RELATIONSHIP TO THE WALL OF A COMBUSTER WITH THE LONGITUDINAL AXIS OF SAID FLAMEHOLDER PARALLEL TO AIR FLOW THROUGH THE COMBUSTOR; AND A FUEL CONDUIT EXTENDING THROUGH SAID STRUT AND THROUGH THE AXIS OF AT LEAST ONE OF SAID BODIES TO TERMINATE AT THE VERTEX OF SAID BODY ON THE UPSTREAM SIDE OF THE AIR FLOW; WHEREBY FLOW OF FUEL THROUGH THE CONDUIT EXITS INTO THE AIR STREAM AT THE VERTEX FORMING A COMBUSTIBLE MIXTURE THAT IS CARRIED OVER THE SURFACE OF THE UPSTREAM BODY TO THE GAP AREA TO REPLENISH THE MIXTURE OF GASES WITHIN THE GAP ESTABLISHING A STABLE RECIRCULATION ZONE AT A PILOTING FLAME. 